The present invention relates to a helical scanning type magnetic recording and reproducing apparatus and, more particularly, to a digital information recording and reproducing apparatus suitable for recording and reproducing a digital audio signal which has been subjected to time base compression.
Helical scanning type digital information recording and reproducing apparatuses include a household video tape recorder known as the 8-mm standard video tape recorder in which a tape pattern such as that shown in FIG. 11 is employed.
In FIG. 11, the reference numeral 1 denotes a video tape, 2 a video track on which a video signal is recorded, 3 a first option track, 4 a second option track, 5 an arrow which indicates a direction in which a rotary head traces, 6 an arrow which indicates a video tape traveling direction, and 7 a track on which is recorded a signal which is obtained by converting an audio signal into a PCM (Pulse Code Modulation) signal and further compressing the time base into about 1/6 of its original value.
The reference symbols .theta..sub.1, .theta..sub.2, .theta..sub.3 and .theta..sub.4 in FIG. 11 respectively denote winding angles of the video tape 1 formed when it is wound on the rotary cylinder, wherein .theta..sub.1 .apprxeq..theta..sub.4 .apprxeq.5.degree., .theta..sub.2.apprxeq. 180.degree. and .theta..sub.3.apprxeq. 30.degree.. The angle .theta..sub.2 corresponds to a period during which a video signal is recorded, while the angle .theta..sub.3 corresponds to a period during which an audio signal is recorded, while the angles .theta..sub.1 and .theta..sub.4 correspond to margins provided for ensuring interchangeability. Accordingly, when this video tape 1 is employed for the purpose of recording only an audio signal, only the area on the video tape 1 indicated by the numeral 7 in FIG. 11 is used for recording, which involves a disadvantageously low efficiency in terms of using the available (effective) area of the video tape to its maximum extent.
In order to overcome the above disadvantage, there is known a system in which, as shown in FIG. 12, the track 2 is divided into five regions B to F, and a time-base compressed PCM signal is recorded in each region in a manner similar to that in the track 7 in FIG. 11 (the track 7 corresponds to the region A in FIG. 12) (this system will be referred to as the "multichannel PCM method", hereinafter). (This system is mentioned in Japanese patent laid-open No. 222402/1983 and European patent application publication No. 0085578). The system increases audio signal recording density by a factor of six compared to that in the system shown in FIG. 11.
However, when the trailing end of the magnetic tape is reached while the audio signal is being recorded in one of the regions, it is necessary that the magnetic tape should be rewound to an appropriate position (in general, the start position of the magnetic tape), and then, the recording is resumed in another region, which fact makes it impossible to effect continuous recording (referred to as the "automatic reverse recording", hereinafter). Further, it involves a long waiting period corresponding to the time required for the magnetic tape to be rewound. Similarly, it is not possible to effect continuous reproduction or playback, and time is lost rewinding the magnetic tape. Further, recording modes include a so-called long play mode (referred to as the "LP mode", hereinafter) in which the magnetic tape traveling speed is reduced to, for example, 1/2, whereby the recording density is made twice as high as that in an ordinary recording mode, namely, the so-called standard play mode (referred to as the "SP mode", hereinafter). It is possible in the LP mode to effect recording over a period of time which is twice as long as that in the SP mode. Since it is possible in the system shown in FIG. 12 to record audio signals in the six regions in the recording modes different from each other, it is necessary to discriminate between the recording modes (SP/LP) at the time of reproduction. However, no consideration is taken in the above prior art.